Host Plants:

On Crops: Lettuce, pea, spinach and many flowers and weeds

Where Found:

Mostly in warm temperate climates, where LMV is transmitted by aphids.

Description:

On young plants, leaves become twisted and partially folded, and grow slowly. When mature plants are infected, mottled patches of yellow and green develop on older leaves, and large leaves close to the head may become twisted. New growth is distorted and slow.

Damage:

Like other plant viruses, lettuce mosaic virus interferes with genetic signaling within the plant. Leaves that are distorted by the virus cannot function normally, so plants struggle to grow and stop gaining size.

Preventing Problems:

Lettuce mosaic virus can be carried on seed, and certified virus-free seed is widely available. In some lettuce-producing areas, only virus-indexed seed may be legally grown. A few varieties also offer some genetic resistance. Measures that reduce aphid populations will cut the risk of this and other viral diseases in the garden. Grow plenty of nectar-producing flowers to attract aphid predators including ladybeetles, lacewings and hover flies. If viral diseases are common in your garden, use row covers (garden fleece) to protect young celery plants from aphids.

Managing Outbreaks:

To keep the problem from spreading, pull up infected plants and compost them. Dispose of any unused seeds, because it is possible the seeds were infected with the virus.